You do not NEED to do anything, but you may or may not want to. If you took the Standard Deduction because your Itemized deductions were not really close to your Standard Deductions then this will not make any difference and there would be no point in trying to amend your return. If you itemized your return depending on how much your Mortgage Insurance Premiums are, it might make a difference and cause you to receive a refund.
If you want to Amend Your Return follow these instructions. You will see your refund/amount due set back to $0, you will then be able to enter the PMI. Your amended return must be paper filed. When you get to the end, it may "appear" that you can e-file it, but it must be mailed. It will take 10-14 weeks for the IRS to process your amended return. Once submitted you can check the status of your amended return here Where's My Amended Return
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